JPH06101463A - Exhaust gas purifying device for engine - Google Patents

Abstract

PURPOSE:To improve durability by improving emission of exhaust gas through promotion of activation of a catalyst and suppression of the increase of the temp of the catalyst and the occurrent of deterioration thereof. CONSTITUTION:Catalysts 16a and 16b are independently arranged at each of single banks LB and RB in a state to approach the exhaust gas port 2b of each bank. When the temperatures of the catalysts 16a and 16b are low, bypass passages 17 and 18 are closed by means of switching valves 19a and 19b. By guiding exhaust gas to the catalysts 6a and 16b right on the downstream side, activation of the catalysts 16a and 16b is promoted by means of an exhaust gas heat and emission of exhaust gas is improved. Meanwhile, when the temperatures of the catalysts 16a and 16b are high, the bypass passages 17 and 18 are opened by means of the switching valves 19a and 19b and exhaust gas is guided through the exhaust gas ports 2b of banks LB and RB to the catalysts 16b and 16a on the other banks RB and LB through the bypass passages 17 and 18. Since exhaust gas is cooled during the flow of it through the bypass passages 17 and 18, the increase of the temperatures of the catalysts 16a and 16b and deterioration and the damage thereof are suppressed and durability is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying apparatus for an engine, which promotes activation of a catalyst at the time of starting and suppresses catalyst deterioration due to the influence of high temperature exhaust gas heat.

[0002]

2. Description of the Related Art Generally, a catalyst used in an exhaust gas purifying apparatus of this type is difficult to activate at a low temperature. Therefore, in order to promote activation at a low temperature start, etc., a catalyst should be installed upstream of an exhaust passage. However, if the catalyst is disposed upstream of the exhaust passage, there is a problem in terms of durability such that deterioration is remarkable under the influence of high temperature exhaust gas heat discharged during high load operation and the like.

Therefore, for example, Japanese Unexamined Patent Publication No. 57-21011
In JP-A-6, two catalysts are arranged at a predetermined interval in one exhaust passage, a bypass passage for bypassing an upstream catalyst is provided, and a switching valve is provided on the upstream catalyst inflow side. When the exhaust gas is at a low temperature, the bypass passage is closed by the switching valve to guide the exhaust gas to the upstream side catalyst, while when the exhaust gas is at a relatively high temperature, the upstream side catalyst is controlled by the switching valve. The technology that aims to improve exhaust gas purification rate and durability by cooling the exhaust gas through the bypass passage by guiding the exhaust gas to the downstream catalyst through the bypass passage. It is disclosed.

[0004]

However, according to this prior art, at least two catalysts are required in one exhaust passage, and particularly in the recent V type and horizontal type engines, exhaust gas purification is performed by a bank. In the case of controlling each of them, at least two catalysts have to be arranged in one bank, which causes a problem of high product cost.

The present invention has been made in view of the above circumstances, and it is possible to improve the exhaust emission by promoting the activation of the catalyst even at the time of starting at low temperature, and prevent the deterioration of the catalyst at high temperature to improve the durability of the catalyst. It is an object of the present invention to provide an exhaust gas purifying device for an engine that not only improves the performance but also reduces the cost of the product.

[0006]

In order to achieve the above object, an exhaust gas purifying apparatus for an engine according to the present invention is close to an exhaust port of an exhaust passage connected to each bank of an engine body having at least two banks. A catalyst is provided at each position, an inlet of the bypass passage is connected between the exhaust port of the exhaust passage and the catalyst, and an outlet of the bypass passage is connected to the other bank. The inlet of the other bypass passage of the exhaust passage communicates with the catalyst, and further, the inlet of the bypass passage is closed and the exhaust passage is closed in each of the exhaust passages when the catalyst temperature is equal to or lower than a set temperature. And a switching valve for closing the exhaust passage and opening the inlet of the bypass passage when the catalyst temperature is equal to or higher than a preset temperature.

[0007]

[Operation] In the above structure, when the catalyst temperature is low, the switching valve provided in the exhaust passage closes the bypass passage, and the exhaust gas is directly guided to the catalyst provided in the exhaust passage communicating with the bank. As a result, this catalyst is heated by the heat of the exhaust gas and its activation is promoted. On the other hand, when the catalyst temperature is high,
The inflow port of the catalyst is closed by the switching valve, and the exhaust gas is guided to the catalyst interposed in the other exhaust passage through the bypass passage. Since the exhaust gas is cooled while flowing through the bypass passage, high temperature deterioration of the catalyst is suppressed and durability is improved.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, FIG. 1 is an overall schematic view of an engine control system, FIG. 2 is a circuit diagram of a control device,
FIG. 3 is a flowchart showing a switching valve control routine.

In FIG. 1, reference numeral 1 is an engine body,
In the figure, a horizontally opposed engine is shown. An intake port 2a and an exhaust port 2b are formed in a cylinder head 2 provided in each of the left bank LB and the right bank RB of the engine body 1. An intake manifold 3 is communicated with the intake port 2a, and a throttle valve 5a is provided upstream of the intake manifold 3 via an air chamber 4.
Is connected to the throttle passage 5. An air cleaner 7 is attached upstream of the throttle passage 5 via an intake passage 6, and the air cleaner 7 is in communication with an air intake chamber 8 which is an intake port for intake air.

Further, an idle speed control valve (ISCV) 10 is provided in an air bypass passage 9 that bypasses the upstream side and the downstream side of the throttle valve 5a.

On the other hand, the exhaust port 2b has an L (left)
An exhaust manifold 11 and an R (right) exhaust manifold 12 are communicated in each bank, and an L exhaust passage 1 is provided at a gathering portion of the exhaust manifolds 11 and 12.
3 and the R exhaust passage 14 are communicated with each other so that the muffler 15
a, 15b.

The banks L are provided in the exhaust passages 13 and 14, respectively.
The L catalyst 16 is provided at a position close to the exhaust ports 2b of B and RB.
a and R catalysts 16b are respectively interposed, and the flow of the exhaust bypass passages 17 and 18 is made between the catalysts 16a and 16b of the exhaust passages 13 and 14 and the collecting portion of the exhaust manifolds 11 and 12, respectively. The inlets 17a and 18a are communicated with each other. The exhaust bypass passages 17 and 18 intersect with each other and extend to the other exhaust passages 14 and 13, and the outlets 17b and 18 of the exhaust bypass passages 17 and 18 are provided.
b is communicated between the inflow ports 18a, 17a of the other exhaust bypass passages 18, 17 opening to the other exhaust passages 14, 13 and the catalysts 16b, 16a. Further, the switching valves 19a, 18a, 18a are provided at the inlets 17a, 18a of the exhaust bypass passages 17, 18 which open to the exhaust passages 13, 14, respectively.
19b are provided respectively. This switching valve 19a,
Reference numeral 19b denotes an L diaphragm actuator 21a and an R diaphragm actuator 21 via the link lever 20.
and b respectively. Each of the diaphragm actuators 21a and 21b is divided into two chambers by a diaphragm, and one of them has a diaphragm spring inside and a switching solenoid valve 22a for controlling the L switching valve 22a and R.
A spring chamber that communicates with the switching solenoid valve 22b for switching valve control is formed, and the other forms an atmosphere chamber that communicates with the atmosphere.

A switching solenoid valve 22 for controlling each switching valve described above.
a and 22b are the diaphragm actuator 21
The spring chambers a and 21b are selectively communicated with the atmospheric port opening to the atmosphere and the negative pressure port communicating with the negative pressure passage 23 communicating with the intake manifold 3. The switching solenoid valve for controlling this switching valve 22a, 22b
The switching operation of is controlled by a control signal output from a control device (ECU) 50 described later. The negative pressure passage 2
3, a surge tank 24 is provided, and a check valve 25 that opens when the negative pressure on the intake manifold 3 side is higher than the negative pressure on the surge tank 24 side.

A switching solenoid valve 22 for controlling each switching valve described above.
When the spring chambers of the diaphragm actuators 21a and 21b are brought to the atmospheric pressure by the control operation of a and 22b, the switching valves 19a and 19b close the inlets 17a and 18a of the bypass passages 17 and 18 and the banks L.
The exhaust passages 13 and 14 communicating with the exhaust manifolds 11 and 12 of B and RB are released. On the other hand, when the spring chambers of the diaphragm actuators 21a and 21b become negative pressure, the switching valves 19a and 19b open the inlets 17a and 18a of the bypass passages 17 and 18 and the exhaust manifolds 11 and 12 of the banks LB and R, respectively.
The exhaust passages 13 and 14 communicating with the valve are closed.

In addition, an injector 26 is exposed immediately upstream of the intake port 2a of each cylinder of the intake manifold 3, and further, for each cylinder of the cylinder head 2.
An ignition plug 27a, the tip of which is exposed to the combustion chamber, is attached, and an ignition coil 27 is provided continuously with the ignition plug 27a.
The igniter 28 is connected to b.

An intake air amount sensor (a thermal air flow meter in the figure) 29 is provided in the intake passage 6 immediately downstream of the air cleaner 7, and a throttle opening sensor 30 is connected to the throttle valve 5a. Has been done.
Further, a knock sensor 31 is attached to the cylinder block 1a of the engine body 1, and a water temperature sensor 33 is exposed to a cooling water passage 32 that communicates both banks LB and RB of the cylinder block 1a. An LO2 sensor 34a and an RO2 sensor 34b are provided in the exhaust passages 13 and 14 just upstream of the catalysts 16a and 16b, respectively, and a catalyst temperature sensor 35 is also provided on the R catalyst 16b.

A crank rotor 36 is mounted on the crank shaft 1b supported by the engine body 1,
A crank angle sensor 37 is provided on the outer circumference of the crank rotor 36.
Are opposite to each other. Further, a cam angle sensor 39 is provided opposite to the cam rotor 38 which is connected to the cam shaft 1c of the engine body 1. The above crank angle sensor 3
7 and the cam angle sensor 39 are not limited to magnetic sensors such as electromagnetic pickups, but may be optical sensors or the like.

On the other hand, protrusions (or slits) are formed on the outer circumferences of the crank rotor 36 and the cam rotor 38, and in the ECU 50, the crank angle sensor 3 is used.
The engine rotation speed and the ignition timing are calculated from the interval period of the pulse detecting the protrusion (or slit) from the cylinder No. 7, and the cylinder from the interrupt of the pulse detecting the protrusion (or slit) from the cam angle sensor 39. Make a distinction.

Further, in FIG. 2, reference numeral 50 is a control unit (ECU) composed of a microcomputer and the like, and the CPU 5
1, ROM 52, RAM 53, backup RAM 54
And the I / O interface 55 are connected to each other via a bus line 56. In addition, a constant voltage circuit 57 is built in the ECU 50.
7 is the battery 5 via the relay contact of the ECU relay 58.
9 and the relay coil of the ECU relay 58 is connected to the battery 5 via the ignition switch 60.
9 is connected. Ignition switch 60
When is turned on, the contact point of the ECU relay 58 is turned on, the voltage of the battery 59 is supplied to the constant voltage circuit 57, and the stabilized voltage is supplied from this constant voltage circuit 57 to each part of the ECU 50. On the other hand, the backup voltage is constantly applied to the backup RAM 54 from the constant voltage circuit 57. A fuel pump 62 is connected to the battery 59 via a relay contact of a fuel pump relay 61.

A battery 59 is connected to the input port of the I / O interface 55 of the ECU 50 to monitor the battery voltage, and the intake air amount sensor 2
9, crank angle sensor 37, cam angle sensor 39, throttle opening sensor 30, water temperature sensor 33, RO2 sensor 3
4b, LO2 sensor 34a, knock sensor 31, and catalyst temperature sensor 35 are connected.

An igniter 28 is connected to the output port of the I / O interface 55, and the R switching solenoid valve 22 is connected via a drive circuit 58.
b, L switching solenoid valve 22a, injector 26, I
The SCV 10 and the relay coil of the fuel pump relay 61 are connected.

A control program, various fixed data, etc. are stored in the ROM 52, and the RAM 5 is also stored.
3 stores the output signals of the above-mentioned sensors and the like after data processing and the data processed by the CPU 51.

In the CPU 51, when the ignition switch 60 is turned on, the fuel pump relay 6 is first operated according to the control program stored in the ROM 52.
1 is turned on to drive the fuel pump 62, and the fuel injection amount, ignition timing, etc. are controlled based on the output signals of the respective sensors, the catalyst temperature Tc is read, and the switching operation for both switching solenoid valves 22a, 22b is performed. To control.

Next, the switching valve control by the ECU 50 will be described with reference to the flowchart of FIG.

In the flow chart of FIG. 3, when the ignition switch 60 is turned on and the ECU 50 is powered on,
In the routine executed every predetermined time, first, in step (hereinafter abbreviated as "S") 101, the temperature Tc of the R catalyst 16b detected by the catalyst temperature sensor 35 is read, and S102 is read.
Then, the catalyst temperature Tc is compared with the preset activation temperature Tcs. If Tc <Tcs, the process proceeds to S103, where Tc ≧ Tc.
If cs, the process proceeds to S105. In S103, the I / O port output value G1 for the exciting coil of the L switching solenoid valve 22a is set to 0, and then the I / O port output value G2 for the exciting coil of the R switching solenoid valve 22b is set to 0 in S104. Get out.

When the I / O port output values G1 and G2 for the switching solenoid valves 22a and 22b become 0, the atmospheric ports of the switching solenoid valves 22a and 22b are opened to the spring chambers of the diaphragm actuators 21a and 21b. Atmosphere is introduced, the diaphragm actuators 21a and 21b retract the link lever 20 by the urging force of the diaphragm spring, and the switching valves 19a and 19b connected to the link lever 20 are connected to the bypass passage 1
The inflow ports 17a and 18a of the valves 7 and 18 are closed, and the exhaust passages 13 and 14 that communicate with the exhaust manifolds 11 and 12 of both banks LB and RB of the engine body 1 are opened (state shown by solid lines in the figure). As a result, the exhaust gas discharged from the exhaust port 2b of each bank LB, RB flows into the catalysts 16a, 16b located at a short distance in the immediate downstream, so that the temperature of each catalyst 16a, 16b becomes the above-mentioned exhaust gas heat. As a result, the temperature immediately rises, the activation of each of the catalysts 16a and 16b is accelerated, the exhaust purification rate is improved, and the exhaust emission is improved.

On the other hand, when it is judged in step S101 that Tc ≧ Tcs and the process proceeds to step S105, the I / O port output value G1 for the exciting coil of the L switching solenoid valve 22a is set to 1, and thereafter, in step S106, the R switching solenoid valve 22b is switched. Set the I / O port output value G2 for the exciting coil to 1 and exit the routine.

When the I / O port output values G1 and G2 for the switching solenoid valves 22a and 22b become 1, the negative pressure ports of the switching solenoid valves 22a and 22b are opened, and the spring chambers of the diaphragm actuators 21a and 21b are opened. Negative pressure from the intake manifold 3 is introduced into the surge tank 24 via the surge tank 24. As a result, the diaphragm actuators 21a, 21b project the link lever 20 against the urging force of the diaphragm spring, and the switching valves 19a, 1 connected to the link lever 20 are connected.
9b is the inflow port 17a, 18 of the bypass passage 17, 18.
A is opened, and the exhaust passages 13 and 14 are closed immediately downstream of the inlets 17a and 18a (indicated by a chain double-dashed line in the figure).

Then, the exhaust manifold 1 in which the exhaust gas is continuously connected to the exhaust ports 2b of both banks LB and RB.
1 and 12 bypass the bypass passages 17 and 18 and are guided to the other exhaust passages 14 and 13, respectively.
It flows into the catalysts 16b and 16a arranged in the nozzles 4 and 13.
As a result, the exhaust gas passes through the bypass passages 17, 18
Since it is cooled while flowing through the
The temperature of a does not rise abnormally, and deterioration and damage of the catalyst can be prevented.

The present invention is not limited to the above embodiment, and for example, the switching valves 19a and 19b are linked to each other,
The switching operation of the switching valves 19a and 19b may be controlled by one actuator.

Further, although the catalyst temperature is directly detected by the catalyst temperature sensor in this embodiment, it may be estimated based on the engine operating state. For example, in the engine warm-up completion state where the cooling water temperature is equal to or higher than the set value, in the high load state or when the air-fuel ratio is lean, the catalyst temperature becomes high, so the catalyst temperature can be estimated based on these conditions. The determination of the high load state is performed by changing the basic fuel injection amount Tp (a value determined by the intake air amount or the intake pipe negative pressure and the engine speed) and the fuel injection amount Ti (the basic fuel injection amount Tp) that represent the load state. The value corrected by the correction term), the throttle opening, or the intake air amount per stroke can be set to a value equal to or larger than the set value.

Further, in this embodiment, the catalysts 16a and 16b are used.
Independent exhaust passages 13 and 14 and mufflers 15a and 15b are provided on the downstream side of the exhaust gas. However, the exhaust passages are merged on the downstream side of the catalysts 16a and 16b, and one muffler is disposed on the downstream side of the merging portion. You may do it.

Further, the exhaust gas from one bank LB (RB) is fed to the catalyst 16b (1) of the other bank RB (LB).
6a), the air-fuel ratio control is performed in the above bank LB.
If the air-fuel ratio feedback correction coefficient on the (RB) side is set based on the detection value of the O2 sensor 34b (34a), the controllability is improved.

[0035]

As described above, according to the present invention,
When the catalyst temperature is low, the exhaust gas having a high temperature is guided to the catalyst, so that the activation of the catalyst is promoted, the exhaust gas purification rate is improved, and the exhaust emission at the time of low temperature starting is improved.

Further, when the temperature of the catalyst is high, the exhaust gas after being cooled through the bypass passage is guided to the catalyst, so deterioration of the catalyst at high temperature, damage, etc. are suppressed and durability is improved. You can

Furthermore, since it is not necessary to increase the number of catalysts, it is possible to reduce the cost of products.

[Brief description of drawings]

FIG. 1 is an overall schematic diagram of an engine control system.

FIG. 2 is a circuit diagram of a control device.

FIG. 3 is a flowchart showing a switching valve control routine.

[Explanation of symbols]

 1 ... Engine main body 2b ... Exhaust port 13, 14 ... Exhaust passage 16a, 16b ... Catalyst 17, 18 ... Bypass passage 17a, 18a ... Inflow port 17b, 18b ... Outflow port 19a, 19b ... Switching valve LB, RB ... Bank Tcs ... Preset temperature

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location F02B 67/00 L 7541-3G 75/10 Z 7541-3G

Claims (1)

[Claims] 1. A catalyst is provided at a position adjacent to an exhaust port of an exhaust passage connected to each bank of an engine main body having at least two banks, and the exhaust port and the catalyst of each exhaust passage are connected to each other. The inflow ports of the bypass passages are communicated with each other, and the outflow ports of the bypass passages are communicated with the catalyst and the inflow port of the other bypass passage of the exhaust passage communicating with the other bank; In each of the exhaust passages, the inlet of the bypass passage is closed and the exhaust passage is opened when the catalyst temperature is equal to or lower than the set temperature, and the exhaust passage is closed when the catalyst temperature is equal to or higher than the set temperature. An exhaust gas purifying apparatus for an engine, characterized in that a switching valve for opening the inflow port of the bypass passage is also provided.